設計模式----建造者模式

爲什麼使用建造者模式

  代碼中，對象是對現實世界物的抽象。一個對象可以含有大量的必要、不必要的屬性，我們在創建實例時，若採用帶參構 造器、getter/setter方法，由於參數過多，很容易引起混亂。 這時，引入構建者模式，可以清晰的觀測到實例化過程中，需要設置的屬性值。
 

什麼是建造者模式

  建造者模式（Builder Pattern） 又名生成器模式，是一種對象構建模式。它可以將複雜對象的建造過程抽象出來（抽象類別），使這個抽象過程的不同實現方法可以構造出不同表現（屬性）的對象。
 

建造者模式的實現

  直接上代碼：

package builder.source.pojo;

/**
 * @author hw
 * @createTime 2018/9/4
 * @dscrb
 */
public class Person {

    //必寫信息
    private String name;
    private String phoneNumber;

    //可寫可不寫
    private Integer age;
    private char sex;
    private String address;
    private Integer height;
    private Integer weight;
    private String job;
    private String salary;
    private String hobby;

    private Person(){
        return
    }
	
    private Person(Builder builder){
        this.name = builder.name;
        this.phoneNumber = builder.phoneNumber;
        this.age = builder.age;
        this.sex = builder.sex;
        this.address = builder.address;
        this.height = builder.height;
        this.weight = builder.weight;
        this.job = builder.job;
        this.salary = builder.salary;
        this.hobby = builder.hobby;
    }
    
    public static class Builder{

        private String name;
        private String phoneNumber;

        private Integer age;
        private char sex;
        private String address ;
        private Integer height ;
        private Integer weight ;
        private String job ;
        private String salary ;
        private String hobby;

        public Builder(){
            this.age = 0;
            this.address = "未設置";
            this.height = 0;
            this.weight = 0;
            this.job = "未設置";
            this.salary = "未設置";
            this.hobby = "未設置";
        }
        
        public Builder(String name, String phoneNumber){
            this.name = name;
            this.phoneNumber = phoneNumber;
            this.age = 0;
            this.address = "未設置";
            this.height = 0;
            this.weight = 0;
            this.job = "未設置";
            this.salary = "未設置";
            this.hobby = "未設置";
        }
        
        public Person build(){
            return new Person(this);
        }
        
        public Builder name(String name){
            this.name = name;
            return this;
        }
        public Builder phoneNumber(String phoneNumber){
            this.phoneNumber = phoneNumber;
            return this;
        }
        public Builder age(Integer age){
            this.age = age;
            return this;
        }
        public Builder sex(char sex){
            this.sex = sex;
            return this;
        }
        public Builder address(String address){
            this.address = address;
            return this;
        }
        public Builder height(Integer height){
            this.height = height;
            return this;
        }
        public Builder weight(Integer weight){
            this.weight = weight;
            return this;
        }
        public Builder job(String job){
            this.job = job;
            return this;
        }
        public Builder salary(String salary){
            this.salary = salary;
            return this;
        }
        public Builder hobby(String hobby){
            this.hobby = hobby;
            return this;
        }        
    }

    //省略Person類中的getter/setter方法 

    @Override
    public String toString() {
        return "Person{" +
                "name='" + name + '\'' +
                ", phoneNumber='" + phoneNumber + '\'' +
                ", age=" + age +
                ", sex=" + sex +
                ", address='" + address + '\'' +
                ", height=" + height +
                ", weight=" + weight +
                ", job='" + job + '\'' +
                ", salary='" + salary + '\'' +
                ", hobby='" + hobby + '\'' +
                '}';
    }
}

  測試代碼：

package builder.source.test;

import builder.source.pojo.Person;

/**
 * @author hw
 * @createTime 2018/9/4
 * @dscrb
 */
public class SetPerson {

    public static void main(String[] args) {
        set();
    }

    public static void set(){
        Person person1 = new Person.Builder().name("小小").age(23).build();
        System.out.println(person1);

        person1.setHobby("看書");
        System.out.println(person1);

        Person person2 = new Person.Builder().age(23).address("高新").height(170).hobby("聽歌").job("IT").salary("111").sex('m').weight(50).build();
        System.out.println(person2);

        Person person3 = new Person.Builder("小胡","13227012222").build();
        System.out.println(person3);
    }
}

  測試結果：

Person{name='小小', phoneNumber='null', age=23, sex= , address='未設置', height=0, weight=0, job='未設置', salary='未設置', hobby='未設置'}
Person{name='小小', phoneNumber='null', age=23, sex= , address='未設置', height=0, weight=0, job='未設置', salary='未設置', hobby='看書'}
Person{name='null', phoneNumber='null', age=23, sex=m, address='高新', height=170, weight=50, job='IT', salary='111', hobby='聽歌'}
Person{name='小胡', phoneNumber='13227012222', age=0, sex= , address='未設置', height=0, weight=0, job='未設置', salary='未設置', hobby='未設置'}

  這種方式最大的好處就是在創建中使用流式創建對象，控制實例變量時需要的屬性。但是，在構建這個類時代碼會很龐大。